After upgrading IntelliJ the old directories still remain unused. I suggest to delete them.
Configuration Files:
~/Library/Preferences/<Tool><Version>
Cache:
~/Library/Caches/<Tool><Version>
Logs:
~/Library/Logs/<Tool><Version>
Plugins:
~/Library/Application Support/<Tool><Version>
<Tool> would be one of the following:
IntelliJIdea (Ultimate) or IdeaIC (Community)